This application is based upon, claims the benefit of priority of, and incorporates by reference the contents of prior Japanese Patent Application No. 2002-92495 filed Mar. 28, 2002.
1. Field of the Invention
The present invention relates to an electronic control unit which is placed in, for example, an engine compartment of a vehicle.
2. Description of the Related Art
In an electronic control unit (ECU), for example, used for control of a vehicle, a microcomputer for performing operational processing, an input/output circuit connected to an external load, a sensor, a power supply circuit for supplying power to circuits, and like components have been conventionally placed on a substrate. Then, these circuits and substrate are housed within an enclosure typically consisting of a case and a cover.
The electronic components constituting the above-mentioned circuits generate heat during their operation. An excessively increased temperature of the electronic components adversely affects the operation of the components. Therefore, in order to reduce a temperature of the electronic components, a method for transferring the heat to the substrate, and the like, so as to diffuse the heat is known.
Moreover, as shown in FIG. 12, for an electronic component (for example, a semiconductor chip of a power transistor) P1 that generates a particularly large amount of heat, a method using a radiator fin P2 or the like has been used to efficiently dissipate the heat generated from the electronic component P1 toward a case P3. However, given current product demands, the electronic control unit has been required to have higher function and performance levels, while the heat generated from the electronic component P1 increases.
Accordingly, in order to dissipate a larger amount of heat from the heat-generating electronic component P1, the structure as shown in FIG. 13 has been adopted. In this structure, a large piece of copper foil P6 is placed on the region where the electronic component P1 (more specifically, a heat sink P5) is attached on a substrate P4. The heat is dissipated via holes P7 to other larger pieces of copper foil P8 and the like. In this method, however, since an effective wiring area on the substrate P4 is decreased, the substrate P4 in a large size is accordingly required, leading to an increase in cost.
On the other hand, miniaturization of the electronic control unit is also desirable. In order to respond to such a need for miniaturization, that is, a method for miniaturizing the components in accordance with the development of semiconductor integration techniques, a method for making a number of circuits IC-compatible and the like have been used. However, the use of such methods causes an increase in temperature of the electronic component P1.
As measures against the increase in temperature of the electronic component P1, it has been proposed to use the expensive electronic component P1 which results in little power loss. Additionally, it has been proposed to mount the components on the radiator fin P2 or to increase the size of the substrate P4 to a certain degree so as to improve heat dissipation. However, these methods result in increased costs.
It is also conceivable to make the heat-generating electronic component P1 itself highly heat resistant. However, such a measure is not necessarily preferable because peripheral components placed at a high density also have an increased temperature due to heat transferred from the substrate P4, whereby the size of the substrate P4 must be increased to a certain degree or the peripheral components must be high heat-resistant components.
The present invention has been developed to solve the above problems, and has an object of providing an electronic control unit having a high heat dissipating ability, which can be easily fabricated at a low cost.
(1) A first aspect of the present invention relates to an electronic control unit. The unit includes a substrate having a mount face (i.e. first) and an opposite mount face (i.e. second), an electronic component that generates heat and is placed on a side of the mount face, and an enclosure consisting of a plurality of enclosure members to house the substrate. A portion of the enclosure members on a side of the opposite mount face is made to protrude toward a position where the electronic component is mounted, while a flexible, thermally conductive material is placed between the protrusion and the opposite mount face so as to be in contact with a side of the protrusion and the side of the opposite mount face. The enclosure member having the protrusion and the substrate are brought to be in direct contact with each other or in contact with each other through a spacer having a predetermined thickness so as to fix the assembly.
Since the flexible, thermally conductive material is provided between the protrusion of the enclosure member and the substrate in an embodiment of the present invention, it ensures close adherence between the enclosure member and the substrate on their large faces through the thermally conductive material. As a result, the heat dissipation properties are enhanced.
Moreover, since the enclosure member having the protrusion and the substrate are brought into direct contact with each other or through a spacer, the dimensional accuracy of a gap between the substrate and the protrusion can be ensured. As a result, since the thermally conductive member placed in the gap can be very small, such a structure contributes to a reduction in cost.
Moreover, even in the case where a thermally conductive material having an inferior thermal conductivity to those of the enclosure or a thermally conductive thin film layer (for example, a copper foil) on the surface of the substrate, the maximum heat dissipation properties can be ensured because the gap can be normally reduced as described above.
(2) According to a second aspect of the present invention, a thermally conductive thin film layer (for example, a piece of copper foil which is a thin, metallic film) having a higher thermal conductivity than that of a periphery thereof, is provided on the mount face so as to overlap a region obtained by projecting the electronic component thereon.
More specifically, the thermally conductive thin film layer is provided so as to (partially or entirely) overlap the region obtained by projecting the electronic component onto the substrate side, whereby the heat transfer properties from the electronic component side toward the substrate side can be enhanced. Although it is preferred that the sentence xe2x80x9cthe thermally conductive thin film layer is provided so as to (partially or entirely) overlap the region obtained by projectingxe2x80x9d means xe2x80x9cthe thermally conductive thin film layer is provided on a half or more of the region obtained by projectingxe2x80x9d in terms of heat transfer properties, it is more preferred that this sentence mean xe2x80x9cthe thermally conductive thin film layer is provided so as to completely include the region obtained by projecting.xe2x80x9d The same is applied to the following.
(3) According to a third aspect of the present invention, a thermally conductive thin film layer having a higher thermal conductivity than that of a periphery thereof is provided on the opposite mount face so as to overlap a region obtained by projecting an end face of the protrusion.
More specifically, the thermally conductive thin film layer is provided so as to (partially or entirely) overlap the region obtained by projecting the protrusion thereon, thereby enhancing the heat transfer properties from the substrate side toward the enclosure side.
(4) According to a fourth aspect of the present invention, thermally conductive thin film layers, each having a higher thermal conductivity than that of a periphery thereof, are provided respectively on the mount face and the opposite mount face so as to overlap a region obtained by projecting the electronic component thereon, and the thermally conductive thin film layers are connected to each other through a hole. Since the thermally conductive thin film layers provided on the mount face and the opposite mount face of the substrate are connected to each other through a hole In an embodiment of the present invention, the heat transfer properties between both surfaces of the substrate can be enhanced.
(5) According to a fifth aspect of the present invention, thermally conductive thin film layers, each having a higher thermal conductivity than that of a periphery thereof, are provided respectively on the mount face, the opposite mount face, and inside the substrate so as to overlap a region obtained by projecting the electronic component thereon.
Since the thermally conductive thin film layers are provided on the mount face and the opposite mount face of the substrate, and inside the substrate In an embodiment of the present invention, the heat transfer properties between both surfaces of the substrate can be enhanced.
(6) According to a sixth aspect of the present invention, an area of the thermally conductive thin film layer on the side of the opposite mount face is formed larger than that on the side of the mount face.
The present invention has advantages in that thermal conductivity can be further improved in a direction from the mount face of the substrate to its opposite mount face and in that the heat diffused to the periphery can be absorbed.
(7) According to a seventh aspect of the present invention, other than the thermally conductive thin film layer corresponding to the region obtained by projecting the electronic component, a thermally conductive thin film layer is provided at another location of the substrate, and the thermally conductive thin film layers are thermally separated from each other.
Since the thermally conductive thin film layers are thermally separated from each other In an embodiment of the present invention, the adverse heat diffusion to the peripheral components can be restrained.
(8) An eighth aspect of the present invention relates to an electronic control unit including a substrate having a mount face and an opposite mount face, an electronic component generating heat that is placed on a side of the mount face, and an enclosure housing the substrate. A part of the enclosure on the side of the mount face is made to protrude toward the electronic component, while a flexible, thermally conductive material is placed between the protrusion and the electronic component so as to be in contact with a side of the protrusion and a side of the electronic component.
In an embodiment of the present invention, the thermally conductive material is placed not on the side of the opposite mount face of the substrate, but on the mount face.
As a result, since the heat can be transferred from the electronic component toward the enclosure side through the thermally conductive material without passing through the substrate, good heat dissipation properties can be obtained so as to restrain the effects of heat on the other electronic components on the substrate. Moreover, the mounting area for wiring and the electronic components on the substrate can also be increased.
(9) According to a ninth aspect of the present invention, the electronic component is in contact with the thermally conductive material through a radiator member that is integrally molded with the electronic component. As a result, heat dissipation can be efficiently performed.
(10) A tenth aspect of the present invention relates to an electronic control unit including a substrate that has a mount face and an opposite mount face, an electronic component that generates heat and that is placed on a side of the mount face, and an enclosure that houses the substrate. A part of the enclosure on a side of the opposite mount face is made to protrude toward a position where the electronic component is mounted, while a flexible, thermally conductive material is placed between the protrusion and the opposite mount face, and at least one surface of the protrusion and the opposite mount face. At least one surface is in contact with the thermally conductive material and is formed to have a concave-convex shape.
More specifically, in an embodiment of the present invention, the flexible, thermally conductive material is placed between the protrusion of the enclosure and the opposite mount face of the substrate, while at least one of a surface of the protrusion and the opposite mount face is formed to have a convex-concave shape.
As a result, the contact area with the thermally conductive material is increased to improve the heat dissipation properties. Therefore, even in the case where an electronic component that generates a large amount of heat is to be mounted, another special structure (for example, an increase in size of the protrusion or the thermally conductive thin film layer) is not needed, thereby contributing to a reduction of the enclosure in terms of size or a reduction in cost.
(11) According to an eleventh aspect of the present invention, a thermally conductive thin film layer having a higher thermal conductivity than that of a periphery thereof is provided on the opposite mount face, while the convex portion of the convex-concave shape is provided on the thermally conductive thin film layer with solder. Since the convex portion is made of a solder in an embodiment of the present invention, the convex-concave shape can be easily formed at a low cost.
(12) According to a twelfth aspect of the present invention, the protrusion having the concave-convex shape is integrally formed with the enclosure. Since the protrusion and the concave-convex shape can be integrally formed by, for example, casting or injection molding, the concave-convex shape can be accurately formed even at a low cost. Moreover, since the dimensional accuracy of the gap between the protrusion and the substrate is enhanced, the minimal, yet thermally conductive material is sufficient for use. At the same time, the heat transfer performance can be maintained at a high level.
(13) According to a thirteenth aspect of the present invention, the convex portion and the concave portion on the opposite mount face are respectively formed so as to correspond to the convex portion and the concave portion on an end face of the protrusion. Since the gap between the protrusion and the substrate can be made uniform in an embodiment of the present invention, the heat transfer performance can be maximized. Moreover, the stress due to thermal expansion can also be made uniform. Furthermore, the minimal thermally conductive material is sufficient for use, while the heat transfer performance can be maintained at a high level.
(14) According to a fourteenth aspect of the present invention, thermally conductive thin film layers, each having a higher thermal conductivity than that of a periphery thereof, are provided on the mount face and the opposite mount face so as to overlap a region obtained by projecting the electronic component thereon, and the thermally conductive thin film layers are connected to each other via a hole. This structure allows the heat transfer properties to be enhanced as described above.
(15) According to a fifteenth aspect of the present invention, thermally conductive thin film layers, each having a higher thermal conductivity than that of a periphery thereof, are provided on the mount face and the opposite mount face and inside the substrate so as to overlap a region obtained by projecting the electronic component thereon. This structure allows the heat transfer properties to be enhanced as described above.
(16) According to a sixteenth aspect of the present invention, other than the thermally conductive thin film layer corresponding to the region obtained by projecting the electronic component, a thermally conductive thin film layer is provided at another location of the substrate, and the thermally conductive thin film layers are thermally separated from each other. This structure prevents the heat from being transferred to the peripheral electronic components and the like, as described above.
(17) A seventeenth aspect of the present invention relates to an electronic control unit including a substrate having a mount face and an opposite mount face, an electronic component that generates heat and that is placed on a side of the mount face and an enclosure housing the substrate. A solid thermally conductive member is placed between the opposite mount face and the enclosure so as to be in contact with a side of the opposite mount face and a side of the enclosure, while a flexible, thermally conductive material is placed between the thermally conductive member and the enclosure so as to be in contact with a side of the thermally conductive member and the side of the enclosure. Since the enclosure, the thermally conductive material, the thermally conductive member, and the substrate are placed in this order, high heat dissipation properties can be ensured.
Moreover, since it is not necessary to provide a protrusion on the enclosure side in advance, the common enclosure can be utilized. Furthermore, even if there is a change in layout of the electronic components and the like, it is not necessary to redesign the enclosure. Thus, such a structure is advantageous with its high general-purpose properties.
(18) According to an eighteenth aspect of the present invention, the thermally conductive member is soldered to the opposite mount face. As a result, heat transfer performance can be ensured. Moreover, in the case where, for example, a ceramic chip and the like is used as the thermally conductive member, the thermally conductive member can be attached to the substrate by a so-called surface mounting technique in the same manner as for the electronic components.
(19) According to a nineteenth aspect of the present invention, at least one surface of the thermally conductive member and the enclosure, the at least one surface being in contact with the thermally conductive material, is formed to have a convex-concave shape. The concave-convex shape increases the contact area with the thermally conductive material as described above, thereby improving the heat dissipation properties.
(20) According to a twentieth aspect of the present invention, the convex-concave shape of the enclosure is integrally formed with the enclosure. As described above, the integral formation allows the concave-convex shape to be accurately fabricated at low cost. Moreover, since dimensional accuracy of the gap between the thermally conductive member and the enclosure is increased, the area used by the thermally conductive member is minimized, while the heat transfer performance may be maintained at a high level.
(21) According to a twenty-first aspect of the present invention, the convex-concave shape of the thermally conductive member is integrally formed with the thermally conductive member. The present invention has the same effect as that of the above-described twentieth aspect.
(22) According to a twenty-second aspect of the present invention, the convex portion and the concave portion of the enclosure are respectively formed so as to correspond to the convex portion and the concave portion of the thermally conductive member.
Since a gap between the thermally conductive member and the enclosure can be made uniform in an embodiment of the present invention, the heat transfer performance can be maximized. Moreover, stress due to thermal expansion can be made uniform.
Furthermore, the minimal amount of thermally conductive material is sufficient for use, while the heat transfer performance can be maintained at a high level.
(23) A twenty-third aspect of the present invention relates to an electronic control unit including a substrate having a mount face and an opposite mount face, an electronic component that generates heat that is placed on a side of the mount face, and an enclosure that houses the substrate. A flexible, thermally conductive material is placed between a part of the enclosure on the side of the mount face and the electronic component so as to be in contact with a side of the enclosure and a side of the electronic component, while a surface of the side of the enclosure in contact with the thermally conductive material is formed to have a convex-concave shape.
Since the heat is transferred from the electronic component side toward the enclosure side through the thermally conductive material without passing through the substrate in an embodiment of the present invention, high heat dissipation properties can be obtained. Moreover, the effect of heat on the peripheral electronic components on the substrate can be prevented. Furthermore, since the convex-concave shape is formed on the enclosure side, the contact area is large, which in turn provides excellent heat dissipation properties.
(24) According to a twenty-fourth aspect of the present invention, the convex-concave shape is integrally formed with the enclosure. As described above, the integral formation allows the concave-convex shape to be accurately fabricated at a low cost. Moreover, since dimensional accuracy of the gap between the thermally conductive material and the enclosure is increased, the thermally conductive material that is used is minimized, while the heat transfer performance is maintained at a high level.
(25) According to a twenty-fifth aspect of the present invention, the electronic component is in contact with the thermally conducive material through a radiator member (for example, a heat sink) that is integrally molded with the electronic component. Since the electronic component radiates heat through the radiator member In an embodiment of the present invention, high heat dissipation properties can be obtained.
(26) A twenty-sixth aspect of the present invention relates to an electronic control unit including a substrate having a mount face and an opposite mount face, an electronic component that generates heat and that is placed on a side of the mount face, and an enclosure that houses the substrate. A part of the enclosure on a side of the opposite mount face is made to protrude toward a position where the electronic component is mounted, while a flexible, thermally conductive material is placed between the protrusion and the opposite mount face so as to be in contact with a side of the protrusion and the side of the opposite mount face. A movement-stopping part protruding toward a side of the thermally conductive material, for preventing the thermally conductive material from moving, is provided on at least one surface of the protrusion and the opposite mount face, the at least one surface being in contact with the thermally conductive material.
Since the movement-stopping part for preventing the thermally conducive material from moving, which is placed on the surface side of the protrusion, is provided In an embodiment of the present invention, the thermally conductive material does not fall out from a space between the protrusion and the substrate. For example, in the case where the thermally conductive material has a low flexibility, for example, in a sheet-like shape, it is suitable to provide convex portions at a plurality of locations in the periphery of the thermally conducive material and at the thermally conductive material itself. On the other hand, in the case where the thermally conductive material has a high flexibility, it is suitable to provide a frame-like convex portion which continuously surrounds the periphery of the thermally conductive material.
(27) According to a twenty-seventh aspect of the present invention, a thermally conductive thin film layer having a higher thermal conductivity than that of a periphery thereof is provided on the opposite mount face of the substrate corresponding to the position where the electronic component is mounted, while the movement-stopping part is provided on a surface of the thermally conductive thin film layer with a solder. In an embodiment of the present invention, for example, a frame-like movement-stopping part can be easily provided at a low cost, without requiring any processing or other components.
(28) According to a twenty-eighth aspect of the present invention, the movement-stopping part is integrally formed with the protrusion. The integral formation facilitates the formation of the movement-stopping part and improves the dimensional accuracy.
(29) A twenty-ninth aspect of the present invention relates to an electronic control unit including a substrate having a mount face and an opposite mount face, an electronic component that generates heat and is placed on a side of the mount face, and an enclosure that houses the substrate. A solid, thermally conductive member is placed between the opposite mount face and the enclosure so as to be in contact with a side of the opposite mount face and a side of the enclosure, while a flexible, thermally conductive material is placed between the thermally conductive member and the enclosure so as to be in contact with a side of the thermally conductive member and the side of the enclosure. A movement-stopping part protruding toward a side of the thermally conductive material, for preventing the thermally conductive material from moving, is provided on at least one surface of the opposite mount face and the thermally conductive member. The at least one surface being in contact with the thermally conductive material.
In an embodiment of the present invention, the thermally conductive member is placed between the opposite mount face and the enclosure, while the thermally conductive material is placed between the thermally conductive member and the enclosure. Moreover, the movement-stopping part is provided on the surface facing the thermally conductive material in contact therewith.
As a result, high heat dissipation properties can be ensured. In the case where the movement-stopping part is provided on the thermally conductive member side, in particular, standardization of the enclosure can be ensured. At the same time, the degree of freedom in substrate designing is improved, thereby largely contributing to a reduction in cost.
(30) According to a thirtieth aspect of the present invention, the movement-stopping part is integrally formed with the thermally conductive member or the enclosure. The integral formation facilitates the formation of the movement-stopping part and improves the dimensional accuracy.
(31) According to a thirty-first aspect of the present invention, the thermally conductive member is soldered onto the opposite mount face.
As a result, the heat transfer performance can be sufficiently ensured. In the case where, for example, a ceramic chip and the like is used as the thermally conductive member, the thermally conductive member can be attached to the substrate by a so-called surface mounting technique in the same manner as the electronic components.
(32) According to a thirty-second aspect of the present invention, thermally conductive thin film layers, each having a higher thermal conductivity than that of a periphery thereof, are respectively provided on the mount face and the opposite face so as to overlap a region obtained by projecting the electronic component thereon, while the thermally conductive thin film layers are connected to each other through a hole.
As a result, the heat transfer properties related to a thickness direction of the substrate can be enhanced, as described above.
(33) According to a thirty-third aspect of the present invention, thermally conductive thin film layers, each having a higher thermal conductivity than that of a periphery thereof, are respectively provided on the mount face, the opposite face, and inside the substrate so as to overlap a region obtained by projecting the electronic component thereon.
As a result, the heat transfer properties related to a thickness direction of the substrate can be enhanced, as described above.
(34) According to a thirty-fourth aspect of the present invention, other than the thermally conductive thin film layer corresponding to the region obtained by projecting the electronic component thereon, a thermally conductive thin film layer is provided at another location of the substrate, while the thermally conductive thin film layers are thermally separated from each other.
Since the thermally conductive thin film layers are thermally separated from each other, the effect of heat on the electronic components and the like at the periphery of the substrate can be restrained.
(35) A thirty-fifth aspect of the present invention relates to an electronic control unit including a substrate having a mount face and an opposite mount face, an electronic component that generates heat and that is placed on a side of the mount face, and an enclosure housing the substrate. A flexible, thermally conductive material is placed between a part of the enclosure on the side of the mount face and the electronic component so as to be in contact with a side of the enclosure and a side of the electronic component. A movement-stopping part protruding toward a side of the thermally conductive material, for preventing the thermally conductive material from moving, is provided on at least one surface of the electronic component and the enclosure, the at least one surface being in contact with the thermally conductive material.
Since the heat is transferred from the electronic component toward the enclosure side through the thermally conductive material and not through the substrate, little heat is transferred to the substrate side, thereby providing high heat dissipation properties. Moreover, thermal effects on the other components mounted on the substrate can be reduced. Furthermore, the movement-stopping part can prevent the thermally conductive material from flowing out.
(36) According to a thirty-sixth aspect of the present invention, the movement-stopping part is integrally formed with the enclosure. Since the movement-stopping part is integrally formed with the enclosure, its formation is simple. At the same time, high dimensional accuracy is obtained.
(37) According to a thirty-seventh aspect of the present invention, the electronic component is in contact with the thermally conductive material through a radiator member (for example, a heat sink) integrally molded with the electronic component. As a result, since the electronic components can radiate heat through the radiator member, the present invention is effective because of its high heat dissipation properties.
(38) According to a thirty-eighth aspect of the present invention, the movement-stopping part is a frame part surrounding a periphery of the thermally conductive material, formed in a convex shape. Since the-present invention prevents the thermally conductive material from flowing out or falling out, the thermally conductive material can be prevented from flowing out even if, for example, the electronic control unit is placed in a longitudinal direction.
Moreover, since the periphery of the position where the thermally conductive material is placed is surrounded by the frame part, it is not necessary to thinly apply the thermally conductive material thereto. The thermally conductive material has an even thickness by merely placing the thermally conductive material within the frame with a simple process (for example, potting the thermally conductive material in a mountainous shape).
A metal material having a higher thermal conductivity than, for example, that of a resin such as an epoxy resin serving as a substrate material and the like can be used as the solid thermally conductive member described above. In view of the thermal conductivity, a general alloy or metal material having a thermal conductivity of 20 to 400 W/mxc2x7K can be used.
The thermally conductive material is, for example, a flexible semi-solid (or a gel) whose shape is easily deformed upon pressing. A silicon-type material having a higher thermal conductivity than, for example, that of a resin such as an epoxy resin serving as a substrate material is used as the thermally conductive material. In view of the thermal conductivity, a material having a thermal conductivity of about 1 to 3 W/mxc2x7K can be used.
A thin film layer made of, for example, a copper foil having a higher thermal conductivity than that of a resin such as an epoxy resin that serves as a substrate material can be used as the thermally conductive thin film layer described above. In view of the thermal conductivity, copper having a thermal conductivity of about 398 W/mxc2x7K can be used.
A solid metal material, for example, having a higher thermal conductivity than that of a resin that serves as a molding material can be used as the radiator member (for example, a heat sink). In view of the thermal conductivity, a general alloy or metal material having a thermal conductivity of 20 to 400 W/mxc2x7K can be used.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.